How high temperatures damage the body

This is how the heat affects the body

The summer heat exhausted. If you take this lightly, you will tip over and - if the symptoms are ignored - even put your life in danger. How does the human body deal with heat?

Short version:


  • When it is hot, blood vessels widen and blood pressure becomes lower. This can even lead to heat collapse, in which one briefly passes out.
  • You lose salts when you sweat. This can lead to heat cramps.
  • It is therefore advisable to refrain from alcohol, smoking and coffee in the heat.
  • Measures that strengthen the cycle are also useful.

Why do we get hot?

The normal human core temperature is always 36-37 ° C. Nevertheless, we quickly get hot in summer, even though the air temperature hardly reaches this value. The reason for this is that the human body, like a radiator, has to give off heat into the environment.

Body temperature should always remain the same; human biochemical processes run most efficiently at normal temperature. If the body temperature is too low, the metabolism comes to a standstill. If the temperature is too high, the proteins lose their function. The loss of function of the proteins can also be observed in eggs: if the egg becomes hot during cooking, it stalls because the proteins in the egg disintegrate.

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How does temperature regulation work in the body?

In order to keep the processes in the body going, the temperature must be precisely regulated. A region in the brain - the hypothalamus - is responsible for this. Heat-sensitive nerve cells are located in the skin, the spine and in the brain, with the help of which we can perceive temperature.

This system is similar to the thermostat of a heater. When the hypothalamus notices that the temperature limit has been exceeded, certain hormones are released and the circulation reacts. The blood is withdrawn from inside the body and circulates closer to the surface, the blood vessels widen. The blood pressure drops because the same amount of blood now has more space in the enlarged vessels. At the same time, the skin begins to produce sweat. When the sweat evaporates, heat is also withdrawn from the skin. The body cools down.

++ More on the topic: 10 interesting facts about sweat ++

When does the heat get dangerous?

Anyone who sweats loses large amounts of salt and there is an electrolyte deficiency in the muscles. The muscle cannot do its job without minerals. When moving in great heat, the muscles begin to ache and a heat cramp develops. If these signs occur, countermeasures must be taken immediately - for example with isotonic drinks and spicy soup. If you ignore the first symptoms and move on in the heat, headache, dizziness and nausea will come along.

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If the blood vessels dilate so much and the blood pressure is decreased so much that the heart no longer receives enough blood to pump it further, the brain is not supplied with sufficient oxygen. Heat collapses: you lose consciousness. Profuse sweating on particularly hot days can be just as dangerous to your health as low blood pressure. The reason for this is the loss of fluids and minerals.

Exhaustion caused by heat is dangerous even without loss of consciousness: in extreme cases, swelling of the brain can cause it to be life-threatening. Anyone who feels signs of heat exhaustion should immediately go to the shade, put their feet up, drink a lot and consume electrolytes.

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In addition, heat increases the risk of other diseases and causes of death. In a meta-analysis of research on heat waves, the World Health Organization (WHO) found that deaths and illnesses generally increase in times of extreme heat.

Who is particularly affected?

  • People aged 75 and over are often particularly affected. There are many reasons for this, such as the reduced blood flow to the skin or the fact that there are more diseases here that make you more sensitive to heat.
  • People with poor circulation also often suffer from the heat.
  • People with poor physical performance and high body weight are also often more prone to heat.
  • Danger of overheating during sport: Especially when endurance is required, as in a marathon, it can easily lead to heat exhaustion.
  • Occupational risk factor: Heavy work clothing or work with heat increase the likelihood of harm to health.

How can you protect yourself from the heat?

On hot days, you should expose yourself to the heat as little as possible. That means airy clothing, a sun hat and sun protection for the skin and as little exercise as possible in the blazing sun. Since the heat sends the blood pressure down, activities that put a strain on the circulation should be avoided. The following substances increase the effect of the summer heat through drainage and lead to the expansion of the vessels:

  • alcohol
  • Cigarettes
  • coffee
  • tea

+++ More on the topic: healthy eating in summer +++

The easiest way to avoid the heat is to stay in a cool room or in the shade. Damp laundry removes heat from the room, just as the evaporation of sweat cools the skin. Cold foot and forearm baths cool the blood circulating under the skin in these areas and thus help to increase blood pressure.

Switching between hot and cold rooms is the worst thing for the circulatory system, and the risk of getting cold increases. The fan provides short-term relief, but can even prevent the body from emitting heat at outside temperatures of over 30 ° Celsius. The good news is that you can train your body - especially your circulatory system - for hot days.

Fitness and light meals are good for your circulation. Regular sauna users also get their bodies used to temperature differences and can endure the summer heat better.

+++ More on the topic: 8 tips for cooling down in extreme heat +++


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Mag. (FH) Axel Beer, Kristin Lerch
Medical review:
Kerstin Lehermayr

Updated on:

Boulant et al: "Role of the Preoptic-Anterior Hypothalamus in Thermoregulation and Fever," in Clin Infect Dis. (2000) 31 (Supplement 5): S157-S161.

Morimoto et al: "The effect of prostaglandin E2 on the body temperature of restrained rats." in Physiol Behav. 1991 Jul; 50 (1): 249-53.

Leyk, D., Hoitz, J., Becker, C., Glitz, K. J., Nestler, K. & Piekarski, C. (2019). Health hazards and exercise-induced overheating interventions. Deutsches Aerzteblatt Online. (last accessed: August 10, 2020)

Cramer, M. N., & Jay, O. (2016). Biophysical aspects of human thermoregulation during heat stress. Autonomic Neuroscience, 196, 3-13. (last accessed: August 10, 2020)

Mora, C., Dousset, B., Caldwell, IR, Powell, FE, Geronimo, RC, Bielecki, CR, Counsel, CWW, Dietrich, BS, Johnston, ET, Louis, LV, Lucas, MP, McKenzie, MM, Shea, AG, Tseng, H., Giambelluca, TW, Leon, LR, Hawkins, E., & Trauernicht, C. (2017). Global risk of deadly heat. Nature Climate Change, 7 (7), 501-506. (last accessed August 7, 2019)

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